Officially, you won't be able to use 2133 MHz, but OEM specifications are known to be inaccurate as BIOS updates and new chips are released. For example, 3rd gen (sort of) Richland chips are 100% FM2-socket compatible but HP doesn't officially support these chips, and I had a hard time finding people that had successfully upgraded to, say, an A10-6700. That said, I can guarantee you you can use 1866 MHz memory with the A10-5700 you have.
About the storage drive, definitely don't replace your 3TB with a hybrid drive unless you have another system to put the old drive in. An SSD for your OS/apps makes much more sense in this day and age, and if it's any difference to you, I'm personally running a 120GB Samsung 840 EVO with a 3TB HDD.